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Introduction to Sensors

Introduction to Sensors. Sookram Sobhan. Overview. What are Sensors? Detectable Phenomenon Physical Principles – How Do Sensors Work? Need for Sensors Choosing a Sensor Sensor Descriptions Temperature Sensor Accelerometer Light Sensor Magnetic Field Sensor Ultrasonic Sensor

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Introduction to Sensors

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  1. Introduction to Sensors Sookram Sobhan

  2. Overview • What are Sensors? • Detectable Phenomenon • Physical Principles – How Do Sensors Work? • Need for Sensors • Choosing a Sensor • Sensor Descriptions • Temperature Sensor • Accelerometer • Light Sensor • Magnetic Field Sensor • Ultrasonic Sensor • Photogate • CO2 Gas Sensor

  3. What are Sensors? • American National Standards Institute (ANSI) Definition • A device which provides a usable output in response to a specified measurand • A sensor acquires a physical parameter and converts it into a signal suitable for processing (e.g. optical, electrical, mechanical) • A transducer • Microphone, Loud Speaker, Biological Senses (e.g. touch, sight,…ect)

  4. Detectable Phenomenon

  5. Physical Principles • Amperes’s Law • A current carrying conductor in a magnetic field experiences a force (e.g. galvanometer) • Curie-Weiss Law • There is a transition temperature at which ferromagnetic materials exhibit paramagnetic behavior • Faraday’s Law of Induction • A coil resist a change in magnetic field by generating an opposing voltage/current (e.g. transformer) • Photoconductive Effect • When light strikes certain semiconductor materials, the resistance of the material decreases (e.g. photoresistor)

  6. Need for Sensors • Sensors are omnipresent. They embedded in our bodies, automobiles, airplanes, cellular telephones, radios, chemical plants, industrial plants and countless other applications. • Without the use of sensors, there would be no automation !! • Imagine having to manually fill Poland Spring bottles

  7. Choosing a Sensor

  8. Temperature Sensor • Temperature sensors appear in building, chemical process plants, engines, appliances, computers, and many other devices that require temperature monitoring • Many physical phenomena depend on temperature, so we can often measure temperature indirectly by measuring pressure, volume, electrical resistance, and strain

  9. Temperature Sensor • Bimetallic Strip • Application • Thermostat (makes or breaks electrical connection with deflection)

  10. Temperature Sensor • Resistance temperature device.

  11. Accelerometer • Accelerometers are used to measure along one axis and is insensitive to orthogonal directions • Applications • Vibrations, blasts, impacts, shock waves • Air bags, washing machines, heart monitors, car alarms • Mathematical Description is beyond the scope of this presentation. See me during lunch if interested

  12. Light Sensor • Light sensors are used in cameras, infrared detectors, and ambient lighting applications • Sensor is composed of photoconductor such as a photoresistor, photodiode, or phototransistor

  13. Magnetic Field Sensor • Magnetic Field sensors are used for power steering, security, and current measurements on transmission lines • Hall voltage is proportional to magnetic field

  14. Ultrasonic Sensor • Ultrasonic sensors are used for position measurements • Sound waves emitted are in the range of 2-13 MHz • Sound Navigation And Ranging (SONAR) • Radio Dection And Ranging (RADAR) – ELECTROMAGNETIC WAVES !!

  15. Photogate • Photogates are used in counting applications (e.g. finding period of period motion) • Infrared transmitter and receiver at opposite ends of the sensor • Time at which light is broken is recorded

  16. CO2 Gas Sensor • CO2 sensor measures gaseous CO2 levels in an environment • Measures CO2 levels in the range of 0-5000 ppm • Monitors how much infrared radiation is absorbed by CO2 molecules

  17. Thank You

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